1. Field of the Invention
The present invention relates to a land grid array socket for electrical connecting an electronic package such as an integrated circuit (IC) chip with a circuit substrate such as a printed circuit board (PCB), and particularly to a connector adapted for receiving a land grid array (LGA) package therein and electrically connecting the LGA package with a PCB.
2. Description of the Prior Art
An IC package having contact pads arranged on a bottom surface thereof in a land grid array is known as an LGA package. The LGA package has relatively low height, which saves valuable space in electronic assemblies.
Connectors for removably mounting an LGA package on a PCB are known as LGA sockets. An LGA socket typically comprises an insulative base, which is positioned between the LGA package and the PCB. The base defines an array of passageways receiving electrical contacts therein. The contacts correspond with the array of contact pads of the LGA package. Each contact has a pair of opposite free ends that project beyond opposite external surfaces of the base. Prior to mounting of the LGA package, the free ends are spaced apart a predetermined distance. The free ends are respectively engaged with corresponding contact pads of the LGA package, and soldered to contact pads on a mounting surface of the PCB. The LGA package is positioned on the base, and the contact pads of the LGA package rest on the contacts of the base. Thereupon, it is necessary to exert a force upon the LGA package to maintain firm electrical connection between the contacts pads of the LGA package and the respective contacts of the base. The force is powerful enough to maintain the electrical connection between the contacts pads and the contacts.
Various LGA sockets comprises a clip slidably mounted on the base to provide the force are disclosed in, for example, U.S. Pat. Nos. 4,504,105, 4,621,884, 5,302,853, and 5,344,334. Referring to FIG. 5, a typical such LGA socket 9 comprises a clip 93 and a metallic lever 92 respectively mounted to opposite ends of a base 91. The end of the base 91 mounted with the clip 93 defines a pair of troughs mating with a pair of corresponding hooks extending from an end of the clip 93. The opposite end of the base 91 forms a pair of braces holding the lever 92.
Opposite lateral sides of the clip 93 are bent slightly downwardly to form a pair of clasping portions. When the LGA socket 9 is not in use, the clip 93 is rotated down onto the base 91, and the clasping portions rest on a top surface of the base 91.
In use, an LGA package 8 is positioned on the base 91. The clip 93 is rotated down onto the LGA package 8, with the clasping portions resting on the LGA package 8. The lever 92 is rotated down, and engages with a free end of the clip 93. The lever 92 thus presses the clasping portions of the clip 93 onto the LGA package 8.
Because the lever 92 presses down on the clip 93, and the clasping portions of the clip 93 press down on the LGA package 8, the lever 92 simultaneously pulls up the end of the base 91 thereat to counterbalance the pressing forces. In addition, the hooks of the clip 93 tend to pull up the end of the base 91 thereat, to counterbalance the pressing forces of the clasping portions of the clip 93.
Generally, the force required for the clasping portions of the clip 93 to firmly retain the LGA package 8 thereunder is considerable. Accordingly, the pressing force applied by the lever 92 on the clip 93 is also considerable. The result is that the pulling up force of the lever 92 is considerable, and the pulling up force of the clip 93 is also considerable.
Said pulling up forces operate on the opposite ends of the base 91 respectively, and the pressing forces of the clasping portions of the clip 93 operate to press a center portion of the base 91 downward. Because the base 91 is made of plastic, it has limited rigidity. As a result, the opposite ends of the base 91 tend to bend upward and the deformation or warpage of the base is generated. The forces applied by the clasping portions of the clip 93 on the LGA package 8 are decreased. The upshot is that firm and reliable electrical connection between the contacts pads of the LGA package 8 and the contacts of the base 91 is diminished.
In view of the above, a new land grid array socket which overcomes the above-mentioned disadvantages is desired.